The finding results from the examination of the genetic makeup of 152 children with bipolar disorder, which can make people susceptible to major mood swings http://dreddyclinic.com/forum/viewtopic.php?f=110&t=33297, and 140 children without the disorder. They linked variations in a gene known as RORB to the kids with bipolar disorder.

"Our findings suggest that clock genes in general, and RORB in particular, may be important candidates for further investigation in the search for the molecular basis of bipolar disorder," the study's co-author, Dr. Alexander Niculescu, of the Indiana University School of Medicine, said in a news release from the publisher of BMC Psychiatry, which has published the findings online.

The gene, which is mainly expressed in the eye, pineal gland and brain, is thought to be tied to the body's circadian rhythm.

"Bipolar disorder is often characterized by circadian rhythm abnormalities, and this is particularly true among pediatric bipolar patients," Niculescu said. "Decreased sleep has even been noted as one of the earliest symptoms discriminating children with bipolar disorder from those with attention-deficit hyperactivity disorder," he added. "It will be necessary to verify our association results in other independent samples and to continue to study the relationship between RORB, other clock genes and bipolar disorder."